1. Field of the Disclosure
Embodiments disclosed herein relate generally to apparatuses and methods for cutting drill pipe from a wellbore. More specifically, embodiments disclosed herein relate to apparatuses and methods for cutting drill pipe using a washover cutting tool. More specifically still, embodiments disclosed herein relate to methods of cutting drill pipe using a cutting tool with a cutter having a radiused surface.
2. Background Art
During workover and well maintenance operations drill pipe and/or tubing may become stuck in a wellbore. Typically, when a drill pipe or tube becomes stuck in a wellbore, a washover tool may be used to washover the stuck drill pipe or tube in an attempt to free the stuck pipe or tube. However, in many instances, the stuck pipe or tube is not freed by the washover operation. In such a circumstance, it may become necessary to cut the stuck pipe or tube, thereby allowing the upper portion of the stuck pipe or tube to be removed from the wellbore. Examples of drill pipe may include, integral jointed tubing and collared tubing.
To cut the stuck drill pipe, an external cutting tool may be lowered over the pipe during the washover operation. Cutters are then actuated to engage the outer diameter of the stuck drill pipe, and as the cutting tool is rotated, the cutters cut the pipe from an outer diameter to an inner diameter. After the drill pipe is entirely cut, a grapple may be used to remove the cut upper portion of the drill pipe from the wellbore.
Engagement of the cutters of the cutting tool with the outer diameter of the drill pipe typically occurs through actuation of a sleeve by a spring of the cutting tool contacting a flat top surface of the cutter. The vertical force applied by the spring through the sleeve of the cutting tool to the flat top surface of the cutter thereby forces the cutter into engagement with the outer diameter of the still pipe. Conventional external diameter cutting tools having flat top cutters have been successful in cutting drill pipe having relatively thin walls. However, drill pipe having relatively thick walls would not make a complete cut because of a reducing spring force as the knife cuts through the pipe. The flat top surface of the cutters resulted in a decreasing horizontal component of the normal force acting on the cutters as the sleeve of the cutting tool continued to contact the flat top surface of the cutter during operation. Thus, if a wall of the drill pipe is too thick or the outside diameter of the drill pipe is too great, then external cutters may not be capable of cutting through the entire drill pipe.
Accordingly, there exists a need for advanced external pipe cutting tools and cutters capable of cutting large diameter and/or thick walled drill pipe.